1. Field of the Invention
This invention relates to magnetic field detectors in general and to magnetometers that employ tuning forks in particular.
2. Discussion of the Related Art
The measurement of magnetic fields has many applications, such as navigating vessels, detecting magnetic metal in security settings, and prospecting for oil and minerals. In these settings there is a long-standing need for inexpensive, low-power apparatus to detect small changes in magnetic fields over large ranges. Existing apparatus are deficient in one or more of these desirable features.
For example, certain microelectromechanical (MEM) magnetometers measure changes in magnetic fields over only a small range of magnetic intensity. Thus, multiple magnetometers, each adjusted to a different range of magnetic field intensity, may be needed to cover a desired range. Also, some magnetometers respond nonlinearly to changes in the magnetic field intensity. Consequently, extensive and complex calibrations are needed to use these magnetometers. In other instances, components of magnetometers can become distorted when moving in response to a change in the magnetic field, thereby altering the physical or electrical response of the magnetometer itself. In still other cases, the fabrication of magnetometers is complex and expensive.
Similarly, other magnetometers like flux gate magnetometers or search coils require large size electrical coils to attain high sensitivities. They also require passing large currents through the coils during measurements, thereby consuming relatively large amounts of power.
Other magnetometers, such as superconducting quantum interference devices, are very sensitive magnetometers, but require cryogenic temperatures to operate. At room temperature, however, state-of-the-art magnetometers are sensitive to only a few tens of micro-Gauss (e.g., 30-70×10−6 Gauss). Such magnetometers are commercially available from, e.g., Honeywell International Inc., Morristown, N.J. (See their website at www.ssec.honeywell.com.) Yet, many applications would benefit from even higher sensitivities at room temperature.
Thus, a need remains in the art for a highly sensitive magnetometer that operates at room temperature. For example, there is a need for a room temperature magnetometer that has a sensitivity of at least one micro-Gauss (1×10−6 Gauss).